Technical Field
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The present invention relates to a direct injection
system internal combustion engine in which the fuel is injected
directly to a combustion chamber and in type in which a spark
is carried out using an ignition plug which is installed to an
upper portion of the combustion chamber, and in particularly
relates to a direct injection system internal combustion engine
in which a recessed portion is provided on an apex face of a
piston and according to an air fluidization an air-fuel mixture
is transported to the ignition plug and a stratification
combustion is carried out.
Background Art
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This kind of the direction injection system internal
combustion engine has known in, for example, Japanese
application patent laid-open publication No. Hei 6-81656,
Japanese application patent laid-open publication No. Hei
10-8967, Japanese application patent laid-open publication No.
Hei 10-30441, Japanese application patent laid-open
publication No. Hei 10-110660, Japanese application patent
laid-open publication No. Hei 10-110662, Japanese application
patent laid-open publication No. Hei 10-169447, Japanese
application patent laid-open publication No. Hei 9-317475,
Japanese application patent laid-open publication No. Hei
10-169447, Japanese application patent laid-open publication
No. Hei 7-293259, Japanese application patent laid-open
publication No. Hei 7-293259, Japanese application patent
laid-open publication No. Hei 11-50847, and United States
Patent specification No. 5878712 etc..
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In the above stated conventional direct injection system
internal combustion engines, to an apex face of a piston a
recessed portion is provided, utilizing this recessed portion
a tumble air flow is formed in a combustion chamber, according
to this tumble air flow a thick layer of the fuel is formed in
a vicinity of an ignition plug.
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However, in the conventional constructions, according to
the tumble air flow there is a possibility in which the fuel
is diffused in the combustion chamber and there is a problem
that the fuel adheres to the apex face of the piston and to a
wall face of the combustion chamber and to an exhaust gas an
unburned hydrocarbon (THC) of a harmful substance is exhausted.
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Further, a fuel injection timing is limited according to
a position of the piston, when an engine rotation number is
varied, it is impossible to select the most suited fuel injection
timing for a fuel consumption performance.
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The present invention has taken an attention to the above
stated problems and an object thereof resides in that a shape
of a recessed portion provided to the piston is devised and a
fuel adhesion to the piston can be reduced and the harmful
substances contained in an exhaust gas can be reduced, further
an improvement of a fuel consumption performance can be devised.
Disclosure of the Invention
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According to the present invention to attain the above
stated object, in an upper portion of a center of a combustion
chamber an ignition plug is provided, and a fuel injector is
provided to a side portion of the combustion chamber in a side
of an air intake valve, to an apex face of a piston a recessed
portion (a groove) is provided along to a flat plane including
the ignition plug and the fuel injector, and further an ascendant
air flow directing for from a lower portion of the fuel injector
toward an upper portion and a normal tumble air flow directing
from the fuel injector toward the ignition plug are generated.
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In preferably, the recessed portion of the apex face of
the piston is formed with a curved face, a tangential line of
the curved face in a side portion of a side of an air intake
valve is constituted to position in a lower from a tip end of
a nozzle of the above fuel injector in a position of a piston
in which a crank angle of an internal combustion engine is 40
degrees before a top dead center.
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Accordingly, the normal tumble flow is led to a wall face
of a cylinder block along to the recessed portion of the apex
face of the piston and is jetted up to a lower portion of the
fuel injector along to the inner wall of the combustion chamber,
and then the normal tumble flow for rotating from the fuel
injector by passing through the ignition plug is generated.
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As stated in above, when the fuel is ridden on the normal
tumble air flow and the fuel is transported to the ignition plug,
a fuel spray is not adhered to the piston but it is possible
to reach the fuel spray at a vicinity of the ignition plug, under
the conditions of a high load and a high rotation, a stable spark
performance can be obtained and it is possible to carry out a
stratification operation to the high load and the high rotation.
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Further, a width of the recessed portion is formed narrow
gradually to direct from the side of an exhaust valve toward
the side of the air intake valve and then it is possible to make
large the jet-up speed of the normal tumble flow, accordingly
the fuel adhesion to the piston can be reduced, further the
transportation of the fuel to the vicinity of the ignition plug
can be carried out surely.
Brief Description of the Drawings:
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- Fig. 1 is a cross-sectional view for explaining a behavior
of an air and an injection fuel immediately after a fuel
injection of a direst injection system internal combustion
engine using a principle according to the present invention.
- Fig. 2 is a whole perspective view showing a construction
of one embodiment according to the present invention.
- Fig. 3 is a piston shape showing one embodiment according
to the present invention.
- Fig. 4 is a piston shape showing another embodiment
according to the present invention.
- Fig. 5 is a piston shape showing a further another
embodiment according to the present invention.
- Fig. 6 is a schematic view for explaining a principle
according to the present invention.
- Fig. 7 is a cross-sectional view showing an air intake
stroke of a direct injection system internal combustion engine
using a principle according to the present invention.
- Fig. 8 is a cross-sectional view showing an ignition
timing of an internal combustion engine of a direct injection
system internal combustion engine using a principle according
to the present invention.
- Fig. 9 is a cross-sectional view showing an ignition
timing of an internal combustion engine of an immediately after
of a fuel injection of a direct injection system internal
combustion engine using a principle according to the present
invention.
- Fig. 10 is a cross-sectional view showing an ignition
timing of an internal combustion engine of a direct injection
system internal combustion engine using a principle according
to the present invention.
- Fig. 11 to Fig. 15 are various embodiments showing a piston
used in the present invention.
- Fig. 16 is a simulation view showing an air-fuel ratio
for explaining effects according to the present invention.
- Fig. 17 is a simulation view showing a behavior of a fuel
for explaining effects according to the present invention.
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The Best Form of Embodiment for Carrying-out the Invention
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The embodiment according to the present invention will
be explained referring to Fig.1 and Fig. 2.
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Fig. 1 is a view showing a construction of a direct
injection system internal combustion engine for explaining a
principle according to the present invention.
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Fig. 2 is a constructional view showing the embodiment
of a direct injection system internal combustion engine using
the principle according to the present invention. The same
reference characters shown in Fig.1 and Fig. 2 express the same
function members.
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To a cylinder block 1, a cylinder head 2 is installed,
and a piston 4, which is provided in a recessed portion 3 of
the cylinder block 1, is provided. A space constituted by the
above stated cylinder head 2 and the piston 4 forms a combustion
chamber 5. The cylinder head 2 has a pent-roof type.
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To the cylinder head 2, an air intake pipe for opening
to the combustion chamber 5 and an air exhaust pipe are formed,
every cylinders, two air intake pipes 6 and two air exhaust pipes
7 are formed. To the air intake pipe 6 an air intake valve 8
is provided and to the air exhaust pipe 7 an air exhaust valve
9 is provided.
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A peripheral edge portion of a side of the air intake valve
in the combustion chamber 5, a fuel injector 10 is installed
to inject directly the fuel into the combustion chamber 5, and
an ignition plug 11 is provided in which an ignition gap is
positioned at a center of a ceiling portion of the combustion
chamber 5. The above stated fuel injector 10 uses a high
pressure swirl type fuel injector having a jet outlet shape to
give a swirl force to a fuel spray 12.
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At an upstream of the air intake valve 8, a flow rectifying
plate 13 for dividing two a flow passage of the air intake pipe
6 in an upper portion and in a lower portion is provided and
in the upstream thereof a flow dividing valve 14 is provided.
The flow dividing valve 14 operates, when a lower portion flow
passage is shut off within a range of 90 degrees and within the
two divided flow passage according to the flow rectifying plate
13 and a flow passage area of the air intake pipe 6 is reduced,
a velocity of a normal tumble flow generated in the combustion
chamber 5 becomes fast.
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When the velocity of the normal tumble flow is unnecessary,
or when much air is inhaled in the combustion chamber 5, it
operates to open the lower portion flow passage.
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The air intake valve 8 and the air exhaust valve 9 are
operated according to a cum shaft (not shown in figure) provided
on the upper portions, and since the piston 4 pushes and passes
through a connecting pin through a hole 4a, it is connected
rotatively together with a connecting rod 15, as a result the
piston 4 can operate upwardly and downwardly by connecting
together with a crank shaft (not shown in figure) through the
connecting rod 15.
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Relating to the shape of the recessed portion (the groove),
as shown in Fig. 3 and Fig. 11, to a mountain type of an apex
face of the piston the recessed portion is formed with a
depression portion having a radius of R and a width of the above
stated recessed portion is formed to be narrow gradually
directing for from a side of the air intake valve toward a side
of the air exhaust valve. In accordance with the provision of
this groove, even when the piston is risen and a capacity of
the combustion chamber becomes small, since the tumble air flow
is maintained fully, it is possible to carry out the
stratification combustion during the high rotation time.
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Further, since the air flow goes around fully to the lower
portion of the fuel injector, there is no generation about a
secondary eddy according to a leakage air flow (this is shut
off by the flow dividing valve) which is leaked from a lower
portion passage of the two divided air intake pipe. With this
fact, the tumble air flow can be maintained fully and the fuel
amount for transporting to the vicinity of the ignition plug
can be made much.
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Further, since the width of the groove is constituted to
be narrow gradually from the side of the air intake valve to
the side of the air exhaust valve, it is possible to make large
the jet-up velocity of the normal tumble flow, accordingly the
fuel adhesion to the piston can be reduced further, and the
transportation of the fuel to the vicinity of the ignition plug
can be carried out further surely.
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This groove is formed in perpendicular to the connecting
pin between the piston 4 and the connecting rod 15 and the pin
inserting hole 5a. As a result, to the rotation of the
connecting rod there generates no unbalance. Further, the
balance in a peripheral direction of the piston can be
maintained.
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The shape of the recessed portion 3 provided to the piston
according to the present invention is not limited to the shape
shown in Fig. 3 but as shown in Fig. 4 it is possible to form
one in which the width of the recessed portion 3 is constant
and further as shown in Fig. 5 to form one in which the recessed
portion 3 is constituted according to a curved face and a flat
face.
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Further, the flat construction of the apex of the piston
can be adopted. This example will be shown from Fig. 12 to Fig.
15.
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In Fig. 12, a groove having an uniform width is provided
with an uniform depth from the sided of the air exhaust valve
of the piston to the air intake valve, and since a shape thereof
is simple, it is possible to process it easily.
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Further, since a thermal distribution of the piston can
be maintained comparatively uniformly, a lowering in the
efficiency is few.
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In Fig. 13, a width of a groove is constituted to be widely
in the side of the air exhaust valve and to be narrow in the
side of the air intake valve. Further, a depth of the groove
is constituted to be deeply in the side of the air exhaust valve
and shallow in the side of the air intake valve.
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In the above construction, it has a merit in which the
air intake from the two air intake valves is joined natural and
one tumble flow can be formed.
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In accordance with the provision of the slope, it has a
merit, when in the lower portion of the fuel injector the tumble
flow becomes the ascendant air flow, since a directional
conversion can be carried out smoothly and the energy does not
lose, accordingly a strong tumble air flow can be obtained.
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In Fig. 14, a cross-section of a groove is not a
rectangular shape as shown in Fig. 12 and Fig. 13 but is an arc
shape. Further, a diameter of the groove is constituted to be
large in the side of the air exhaust valve and to be small in
the side of the air intake valve. In this construction, it has
merit in which, since the groove can be processed only a rotation
grinding, a good working performance can be obtained.
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Further, it has a merit in which, since the groove has
no corner portion, the air flow in the groove can be formed
smoothly, a fluid loss can be reduced, and accordingly a further
strong tumble flow can be generated.
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In Fig. 15, in a groove a gradient having a curvature from
the side of the air exhaust valve to the side of the air intake
valve is provided. According to this construction, the air flow
is guided smoothly by the air along to the curvature and further
the fluid loss can be reduced, accordingly a strong tumble air
flow can be obtained.
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In this embodiment, as shown in Fig. 6, a tangential line
L in a side end portion of the air intake valve of the curvature
face for forming the recessed portion is positioned in a lower
portion from a tip end of the nozzle of the fuel injector 10
in a position where the piston is 40 degrees before the top dead
center, and a position where a side end portion of the air exhaust
valve for forming the recessed portion and the apex face of the
piston are intersected is positioned in the side of the air
exhaust valve from a position of an electrode position of the
ignition plug 11.
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Further, as shown in Fig. 3, the present invention have
the features, which are the width of the recessed portion forming
narrow directing for from the side of the air exhaust valve to
the air intake valve, when the piston position is the position
where the crank angle is before the top dead center of the crank
angle is 40 degrees, a connecting position between the recessed
portion in the side of the air exhaust valve and the apex face
of the piston is lower than a center line of the fuel injection,
with the above stated crank angle when the fuel is injected,
the recessed portion shape having a largeness of the width where
the fuel is not run over.
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Next, the operation of this embodiment will be explained.
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In a low load operation time, to improve the fuel
consumption performance, a fuel injection amount is made of the
air-fuel ratio of 40. When the air-fuel ratio is 40, the
air-fuel mixture is mixed homogeneously the surrounding portion
of the ignition plug becomes thin excessively and then the spark
can not carry out, it is necessary to carry out a stratification
operation by gathering and burning the air-fuel mixture having
a thick fuel part with a stratification performance state.
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In this embodiment, to carry out the stratification
performance, in the combustion chamber 5 the normal tumble flow
is generated and according to this normal tumble flow the fuel
is transported to the ignition plug 11 and accordingly the
stratification performance can be realized.
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As shown in Fig. 1, when an engine rotation number is 1400
rpm and an average valid pressure in the combustion chamber is
320 Kpa (kilo-Pascal), before 70 deg before the top dead center
the fuel is injected ((1)) and the fuel is ridden on the tumble
air flow and is transported to the position of the ignition plug.
After about 3.12 msec the fuel reaches to the surrounding portion
of the ignition plug and this time just the ignition plug becomes
a spark timing (35 deg before the top dead center) ((2)).
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Further, when then engine rotation number is 3200 rpm and
the average valid pressure in the combustion chamber is 350 Kpa
(kilo-Pascal), 90 deg before the top dead center the fuel is
injected ((1)) and the fuel is ridden on the tumble air flow
and is transported to the position of the ignition plug. After
about 3.0 msec the fuel reaches to the surrounding portion of
the ignition plug and this time just the ignition plug becomes
a spark timing (30 deg before the top dead center) ((2)). (This
is called as a tumble guide system).
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When in the various kinds operation areas, a time from
the fuel injection to the spark timing has measured, it was
understood that the time was within a range from 3 msec to 3.15
msec.
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As a result, in this embodiment, in the area in which the
stratification operation is carried out, in regardless of the
rotation number and the load, the fuel can be injected with the
ignition timing from 3 msec to 3.15 msec.
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As stated in above, in this embodiment, since the fuel
is transported in the combustion chamber with a very short route
to the surrounding portion of the ignition plug, it can be lessen
the possibility about the fuel adhesion to the inner wall of
the combustion chamber and to the piston.
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This manner was simulated and the simulation results were
shown in Fig. 16 and Fig. 17.
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The conditions were that when the engine rotation number
was 3200 rpm and the average valid pressure in the combustion
chamber is 350 Kpa (kilo-Pascal), 80 deg before the top dead
center the fuel having an average particle diameter of 16.3
micron wad injected (the injection period of 1.73 msec).
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The air-fuel ratio was 40 (the air of 496 mg / the fuel
of 12.4 mg), an installation angle (confer Fig. 6) of the
fuel injector was 36 degrees an injection angle o (confer Fig.
6) was 70 degrees, the strong of the tumble air flow (between
one reciprocation of the piston in the combustion chamber, the
air rotates 1.95 rotations) was 1.95.
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A decomposition view shown in Fig. 16 shows a variation
of a rate f/a (fuel/air) of the fuel and the air every 10 deg
after the fuel injection.
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A white portion is a portion of the fuel of 100%, a blue
portion was a portion of air of 100%, and in an intermediate
portion it shows that the fuel becomes small in series.
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At an angular portion in a center since the ignition plug
is installed, at the time point of the 30 deg before the top
dead center (a lower stage center) it was understood that the
fuel was not contact to the piston but gathered the surrounding
portion of the ignition plug.
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In a lower stage right end, the time point of 30 deg before
the top dead center the ignition was not carried out but leaving
as it was the behavior of the fuel was simulated. It was
confirmed that in this time point the tip end of the fuel was
trying to swirl along to the groove of the piston and the effect
of the tumble air flow was left.
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In other words, in the compression stroke, in accompany
with the lapse of the time, the piston is raised, in accordance
with the provision of the recessed portion the normal tumble
flow 16 can be preserved fully.
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Further, as shown in Fig. 3, when the width of the recessed
portion 3 is formed narrow gradually directing for from the side
of the air exhaust valve to the side of the air intake valve,
the two normal tumble flows from the two air intake valves are
gathered according to the recessed portion 3, in the lower
portion of the fuel injector 10, the velocity of the normal
tumble flow 16 which was brought together with one becomes fast.
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The above normal tumble flow 16 can prevent the fuel
adhesion to the piston 4 by lifting up the fuel spray 12 toward
an upper direction and, as shown in Fig. 8, without the
scattering of the vaporized fuel and the air-fuel mixture 17
is transported to the ignition plug. And, the air-fuel mixture
air 17 is performed to the stratification performance and in
the ignition timing it can be sparked stable.
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In this embodiment, according to the normal tumble flow
16 the fuel is transported to the ignition plug 11, however even
the fuel injection start timing becomes faster in the normal
tumble flow a flow pattern is not varied. Since the velocity
of the normal tumble flow 16 increases, the time for transporting
becomes short suitably, in a middle rotation time and in the
high rotation time, it is possible to transport stable the fuel
to the ignition plug 11, accordingly the fuel adhesion amount
to the piston can be reduced.
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In case a low load and a low rotation time, since one cycle
time becomes long, to prevent the fuel scattering the most suited
fuel injection start timing becomes slow. Further, in
proportion to the rotation number, the air flow velocity of the
normal tumble flow 16 becomes small, however in this embodiment
since the normal tumble flow 16 exists, the transportation of
the fuel can be carried out surely.
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In particularly, in this embodiment, to prevent the fuel
scatter, in the piston position of 40 deg before the top dead
center of the crank angle, which is the fuel injection start
timing in the low load and the low rotation area, the tangential
line of the end portion of the air exhaust valve side of the
recessed portion of the piston is formed lower from the center
line of the fuel injector 10 and further is provided to have
a width having a recessed portion shape in which injected fuel
spray is not run over from the recessed portion 3.
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Accordingly with the above construction, the fuel
adhesion to the apex face of the piston 4 in the side of the
air intake valve from the recessed portion 3 can be prevented
and the run-over and the scattering of the fuel from the recessed
portion can be prevented.
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Further, according to the above construction, in response
to the engine rotation number, since the strong of the tumble
air flow is varied proportionally, even the case of the high
rotation time, it is possible to select the most suited injection
timing regardless of the position of the piston.
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Fig. 9 shows the state in which prior to the ignition
(spark) timing the fuel is injected from the fuel injector and
the fuel is ridden to the tumble air flow.
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Fig. 10 shows the state of the ignition timing after about
3 msec (* the engine rotation number of 1400, the average valid
pressure in the combustion chamber of 320 kilo-Pascal and 35
deg before the top dead center, ** the engine rotation number
of 3200, the average valid pressure in the combustion chamber
of 350 kilo-Pascal and 30 deg before the top dead center) and
the fuel spray 17 is just transported to the surrounding portion
of the ignition plug.
Industrial Utilization Applicability
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The present invention in which the recessed portion (the
groove) shape provided to the piston and formed with the most
suited one is utilized to the direct injection system internal
combustion engine and also it can utilize to the piston itself.
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Further, the present invention can be applied to the
direct injection system internal combustion engine in which the
apex portion of the piston is formed with a flat shape.
